Circulating liquid heater



Feb. 1, 1944. .1. B. SANDO IGIRICULATING LIQUID HEATER Filed May 7. 1941 6 Sheets-Sheet 2 Feb. 1, 1944. J. B. SANDO CIRGUL ATING LIQUID HEATER Filed May'7, 194].

JOSEPH B. SANDO BY W2 Fwfl A INVENTOR.

TTORNEY 6 Sheets-Sheet 3 l I I Feb. 1, 1944. J. B. SANDO 2,340,430

CIRCULATING LIQUID HEATER Filed May 7, 1941 6 Sheets-Sheet 5 INVENTOR JOSEPH B. SANDO ATTORNEY Patented Feb. 1, 1944 UNITED STATES PATENT omomarhiiilito HEATER JosephB. Sande, Kansas City, -Mo., assignorto Western LaundryMachinery Company, a corporation of Missouri Application May 7, 1941, Selial 'No. 392;2'95

, 31' Oiaims.

My invention relates to liquid heating devices, and more particularly to aliquid' heating device for circulating 'afluidbetween itself and apparatus to be heated thereby, in a manner such that the fluid leaves the "heating device under a; predetermined pressure and returns to theflheating' device atatmospheric pressure.

It is a purpose of my invention toprcvidean apparatus forheating a "material that is liquid, within the range of temperatures to which the same is heated for use as a heating medium; and which liquidmay be'ofa character that the same will lose its fluidity, or'even solidify, at temperatures'of the atmosphere in the room, or other space, in which the heating apparatus andthe apparatus 'to be heate'dby the'liquid islo'cated, said heating apparatus being provided with means for preventing such immobility or solidification of the heat transfer medium.

It is aparticular purpose of my invention to provide means for heating a heattransfer medium, which is normally in "a iiquidform in use, which heating means is provided with means for maintaining the *heat'transfer medium, in a liquid state, within a predetermined relatively narrow range ofmaximum "and minimum temperatures, considerablyaboveitheboiling point of water, and with 'meansfonmaintaining saidmediumin a "liquid-stateat atemperature above the temperature atWhich saidheat' transfer medium Will'bB- come substantiallyimmobile, or will solidify, to thusprevent the clogging of the system, comprising conduits "extending between the "heating 'means and-the apparatus tobe heated by the heat transfer medium and any chambers, passageaior other spaces, inwhich" the heat transfer medium may be contained in the'apparatusthat is'tobe heated by the heattransfer-medium, due to such solidification or increasein yiscosity of the heat transfer medium to a point of substantial 'immobility, said last mentioned means maintaining the heat 'transferme'dium at 'a' temperature much lower than that whichmight be referred to as the operative temperaturefthereof when the apc paratusis"activelyin use forheatinga pi'ecegfor pieces, or apparatus, "by means of'the heat transfer medium in its liquid state. v

The invention further comprises means for selectively' controiling'the same, so that the heating apparatus will 'maintain the heat transfer mediumat either the higher or the lowerrange of temperatures above referred to, as may be desiredywith means for indicating Whichpf "the temperature ranges hasjbeen selected by the'j sel'ective means, andw'ith "mean independent of said controlling means for halting the eperatmn of the heating means above -a predeterhiined-maximum temperature below the -boii i'ng poirit" ef=the liquid heat-'transfer-+medium.

It is a furtherpurpo'se of my invention to vide new and improved means for heatinga" transfer medium in a'li'quid 's'tatefcomprisin'g a combustion chamber, fluid fueI burnerS; such as gas burners, for heating 'said-medium -en teri-ng said combustion chamber, and means undenthe selective control of temperature responsiverrieans for controlling the supply (bf-fuel -to-sai'd'-burners, for maintaining a draft through -the apparatus to obtain the I highest efiicieney in the transfer of heat from the products of cpmbustion to t l-ie heat transfer-medium, and for cqntrolling'the operation of liquid heat transfer medii-im-oirohla-ting means, whereby the sameis put --undr pressure and is-brought in heat transfer relation to the products of combustion in a highly efficient-manner.

It is a further purpose or-m invenuen to provide in an apparatus of thea'bove mentioned character, means for' heatinga liquid heat trans-- for mediumcomprising a yes'sel in -whic'h said heat transfer medium is caused to 61 c-i ilate; which contains dues, ;or passages, 4 for th'e prodnets of combustion above referred to; and which is in communication with conduits mounted vvithin the tubular or flue like members that are connected in seriesso as-toprovide a'circuitouspath for the heat transfer mediu'mysaid circuitous path leading from the interior of said vessel through the multiplicity of passages for the'products of combustion to a discharge conduit leading tothe apparatus that is to behea ted'bythe heattrans fer medium ,whereby 'the'heat transfer medium is preheated in the vessel by theproducts f'com busti'on jrom-thelconi'bustion chamber, and 's 11introduced intothe' circuitouslyarranged pond its, to be furtherhe'ated and dischargedatthetinperature desired under the control of the "Wmpearaturegres onsive meansafter such heating a a iprqgressively "increasing temperature as heat transfer mediuinpassesfrom one end 1; other end of this circuitous passage.

It is a'fur'ther purposefofinventidntoprovid a fl heatin means Qf fthe above tio'ned ;cliaracter, comp'i irig a"c'o1letin'g cham belt; or sump, receiving the heatQtranSfe'rZfm dli m returned from "the apparatus Cheat d g which is vented so as to maintain i the" thereofat atmospheric pressure rid to means ebmpri g a i i pfiv t d awi g liquid from thes'ump oriiquidrecivingmeana'and in troducing the same under a predetermined pressure into the heating apparatus, said introduction, being, preferably, into the lower portion of said vessel, and the circuitous conduit means for heating the heat transfer medium being connected with the upper portion of said vessel.

It is still a further purpose of my invention to provide means for maintaining the circulation of the heat transfer medium and the draft in the apparatus after the operation of the burners at the operating temperature for the heat transfer medium has ceased, so as to utilize the heat that is in the combustion chamber walls to heat the entire mass of heat transfer medium to a temperature above that maintained while under the influence of the lower temperature control, to thus economize in the use of fuel in heating the heat transfer medium to the operatingtemperature and maintaining the heat transfer medium in a liquid condition after shut down of the apparatus heated, thereby, said means Comprising a controlling element that will maintain the pump and the fan controlling the draft in operation independent of the fuel burners after the fuel burners have been put out of operation by the operating or high temperature control, or by the switching from the high temperature control to the low temperature control.

It is an important object of my invention to provide means for controlling the operation of the fuel burners, which comprise pilot lights, in a manner to prevent any accidental explosion due to combustible gases released by the fuel burners, saidmeans comprising means for creating a spark at frequent intervals, so that if the pilot light should at any time cease to function temporarily because of an interruption in gas pressure or an undue decrease in gas pressure, only a very smallamount of gas canescape therefrom before the same is ignited, and said means further comprises thermostatic means unde r the control of the pilot light flame, or flames, preventing operation of the main thermostatically controlled gas supply valve for the burners to openthe same, unless said pilot lights are in o er i I It is another purpose of my invention to provide means for creating a circuitous path for the heat transfer medium in the heating vessel, and a circuitous path for the products of combustion through the fines, or passages, provided for the same in said heating vessel.

,It' is an important purpose of my invention to provide a device of the above mentioned character, which is a self-contained unit that can be placed in any convenient location adjacent laundry machinery, or other machinery that requires heating by a liquid or similar medium, this being possible due to the provision of the fan for creciting a draft suflicient to obtain complete combustion in the combustion chamber and to circulate the products of combustion through the apparatus and to a, discharge stack, which is of such a character that it can be placed in any location without the necessity of providing a tall and expensive stack.

Other objects and advantages of my invention 'will appear as the description of the drawings proceeds. I desire to have it understood, how 'ever, that I do not intend to limit myself to the particular details shown or described, except as defined in the claims.

' In the drawings:

" Fig. 1 is a view in side elevation partly broken away, of my improved heating apparatus.

Fg. 2 is a view partly in top plan and partly in section taken substantially on the line 2 -2 of Fig. 1, and showinga fragmentary portion of apparatus heated by the heat transfer medium.

Fig. 3 is a fragmentary vertical sectional View through the heating apparatus adjacent one end of the heating vessel.

Fig. 4 is a similar View to Fig. 3, adjacent the other end of the heating vessel.

Fig. 5 is a vertical lon-gitudinalsectional view through the heating vessel.

Fig. 6 is a section taken on the line 66 of Fig. 5. r

Fig. 7 is a vertical sectional view through the sump, or receiver, showing certain associated parts in elevation and partly broken away.

Fig. 8 is a front elevational view of the heating apparatus.

Fig. 9 is a detail vertical sectional view through the fuel control valve for the burners, part of the electrical apparatus associated therewith being shown diagrammatically.

Fig. 10 is a fragmentary section, showing one of the thermostatic elements used for controlling the heating apparatus.

Fig. 11 is a diagrammatic view showing the circuit connections used in the control'of the oper-- ation of the heating apparatus, and

Fig. 12 is a fragmentary view partly in section and partly in elevation of one of the burners.

Referring in detail to the drawings, in Fig. 1 is shown a heating apparatus that is provided with a housing 2| Within which is provided a combustion chamber 2| having walls of refractory material 22. Fuel burners 23 extend into the combustion chamber 2| and the products of combustion pass from the combustion chamber 2| into flue-like members 24, which are shown more in detail in Figs. 3, 4, 5 and 6, and into a chamber 26 that provides a passage leading from the fluelike members 24 to the flue-like members 25, the substantially horizontally extending portion 21 of the wall of refractory material providing a partition between the combustion chamber 2| and the stack chamber 28, which is also provided with walls of refractory material 29, the top wall having an opening therein through which the flue pipe 30 extends to the inlet connection 3| of a blower, or fan, 32, the outlet of which is con nected with a stack 33, which may be of any convenient height to pass the products of combustion out of the building in which the heating apparatus is located. The blower, or exhaust fan, is operated by means of a motor 34, through any suitable driving means, such as the pulleys 35 and .36, the belt 37 and the drive shaft 38, on which the'pulley 36. is mounted. 1

The flue l'ike members 24 and 25 extend through a heating vessel that has a cylindrical wall 39 and end walls, or heads, 40 and 4|, into which the tubular outer wall portions of the fluelike members 2A and 25 are secured in fluid-tight relation, by welding or in any other suitable manner. The products of combustion will accordingly passfr'om the combustion chamber 2| into the interior of the vessel made up of the cylindrical wall 39 and the walls, or'he'ads, 40 and 4|, within the flue-like'members' 24,'then into the end chamber 26 and through the flue-like members 25 to the flue chamber 28 and then through the outlet pipe, or flue, '30, and the fan, or blower, 32 to the stack 33.

The members 24 and 25 are identical in construction and each comprises an inner tubular P a d wer t Witt 5. 3.?

aeronautween which substantially radially extending members 44 extend to mount the tubular member '42 co-axially with the tubular member 43 in'spaced relation thereto,'thus providing amultipl-icity of similar parallel passages 45 for the products of combustion in an annular series around each inner tubular member 42, and a plurality of heat conducting walls connecting said tubular members 42 and 43, rings 34! being provided for'mounting the members 44 in position. The passages within the inner tubular members 4-2 are-shut off from the gases, or products of combustion, passing through the passagesfi, as will be obvious as the description proceeds. The chamber 26 is provided with metallic walls 45 and both the cylindricalwall portion 39 of said vessel and the metallic wall portions 46 of the chamber 26 are-provided with a heat insulating covering 47,and spacedfrom the heat insulating covering of the cylindrical wall portion 39 is a sheet metal housing 48, which is a continuation of the housing so, and extends over the upper portion ofthe vessel having said tubular wall 39, being mounted in spaced relation thereto by means of the angular brackets 49. The flue connecting chamber-2t has a refractory wall portion Sillying outside the insulating wall at and is providedwith a sheet metal outer covering which also extends over the insulating material 41 on the lower portion of the cylindrical wall 3%.

Mounted below the above referred to vessel is a liquid container52, which acts as a receiver for the liquid that is to be heated and which has returned from the apparatus that is heated by means of the liquid, said liquid container being a tank-like member and being mounted on the framework members '53, which, of course, also support'the refractory material of the combustion chamber 2! and other parts of the apparatus.

Transverse frame members 54 also are provided, connecting the' longitudinal framework members 53, and upstanding frame members 55 are provided, mounted on the frame members 53 for supporting various parts of the heating ap paratus and the housing therefor, suitable frame members being mounted on'the vertical frame members 55 for sup-portingjthe refractory material 22 and for supporting the vessel having the cylindrical wall portion 39, as well as the wall portions of the chambers 26 and 28. The tank-like member 52 is provided with a suitable gauge56 to indicate the level of the liquid therein in the usual-manner, and is of a generally rectangular character, with the fiat bottom wall 51 thereof mounted on the transverse frame members 54 and having a flat top wall 58 through which a pair of vent pipes 59 and 69 extend, said vent pipes being secured in liquid-tight relation to the top wall of the tank and communicating'with the chamber provided within the tank52. A tubular container Si is secured in liquid-tight relation with the vent pipes'59, and 60 above the top of the vessel having the cylindrical wall 39, and a vent pipe 62 terminating in an elbow 63 is connected withthe upper side or the tubular member BI, while the vent pipes59 and 60 are with-the lower portion thereof.

' A return pipe 84 forthe liquid that'serves as a heat transfer medium leads into the lower por- 'tion of the one side wall of said tank member '52 and a suction conduit 65 extends-from the re-'- turn pipe adjacent said tank 52 totheinlet side o'f the pump 66, which has the discharge pipe '61 extendingtherefrom, said pump being operated by means ofa motor 68 -througha suitable connected driving means comprisingzthe ul1eys 369 and lorrotating with the motor van'dpump ashafts; respectivelygthe driving belts-T l operating over said pulleys. Said motor and pump are suitably mounted on transverse frame vmembers l2 and T3, respectively, "which are connected with' the vertical frame members 55 by'means of longitudinal frame members 714.

The pump discharge pipe 61 is provided with a T15 connecting the same with a pipe *l6,whlch leads through suitablepipeconnections' to afilter ll. Mounted'within the T T5 is a thermostatic element from whichsuitable conductors ina 'conduit 78 extend, said thermostatic element :and its function being describedin more detail below. From the filter ll a-liquid conduit 19', whiclris made up of pipe and pipe fittings of suitable character, leads into the bottom of the vessel having the cylindrical 'wall 39 through an-in let connection 822 that'leads into the chamber provided between the heads 49 and 4| and said tubular wall. Secured in fixed positio'n within S the chamber provided within-said vessel are the leafflemembersil! .and 82-, said baillernembers 8| being secured to the cylindrical wall 39 front-the bottom portion thereof to withina desired spacing from the top portion thereof to leave passages between the top'edges-of the baffles 8! andsaid cylindrical wall, while the baiile members EZ- are secured to said cylindrical wall and extend from the top portion thereof down to near the bottom part of said container, the'bottom :edges thereof being spaced from the cylindrical Wall so as to provide passages between, the sameand said bylindrical wall at'the bottom of said container. Thus a circuitous passage is provided within the container, or vessel, for'the liquid heat transfer medium extending from the inlet connection to the discharge oroutlet connection 83.

Apipe a l is connected with said outlet connection and with a T 85, a valveiljfi being connected with the top opening of the T85 and being interposed between said T and a pressure gauge ill, while a liquid conduit 88 extends from the side opening of the T '85, beingma'de up of a plural-- ity of fittings and pipes and'leading'through a suitable connection; such as a union '89, in-toone of the tubular members 42, of the upper flue members 25. In order that the path of the liquid through the various pipes 42 can be more readily followed, each of the passages'within said pipes is designated by a dilferent referenc'einumeral, the passage into which the pipe '88 leads being designated by thenumeral 9i. 'SaidJpipe 42 is connected with the next adjacent pipe-42 having the passage 92 therein, by means of a U-shaped pipe connection or return bend 9.3, which is secured to said pipes 42 by means of suitable unions 89, said connection being made within the flue chamber, or flue box, 23. It will be noted that the conduit 83 passes through the walls of the chamber 25 and that .the connection with the tubular member 42 having the passage dl is made within the chamber at. The passage $2 is thus connected in series ,with the passage ill. The passage 94 is similarly connected inserieS with the passage 92 through a U-shaped tubularmember, or return'bend,v 95.

'Howeven the return bends at this end of the app'aratus are no't'connected with the tubular members by means of unions, but are permanently secured thereto, as by welding, or the adjacent bers 42 is connected with the passage 94 by means of a U-shaped connecting member, or return bend, 91, in a similar manner to that already described. The passages 98, 99 and I99 in the upper tier of tubular members are connected in series at the opposite ends thereof by means of the return bends I,9I, I92 and I93, respectively. It will thus be seen that the tubular members 25 that comprise the upper tier of flue-like members connecting the chamber 26 with the chamber 28, have liquid conduits therein, the passages of which are connected in series so that the liquid will flow back and forth in a circuitous path in the inner pipes, or tubes, 42 of said flue-like members, the passages, or tubes, 42 in the adjacent fiue-like members having the liquid there in traveling in opposite directions.

A large U-shaped connecting portion, or return bend, I94 connects the passage I99 in the last of said upper series of tubular liquid conduits with the passage I95 in the tubular member 42 immediately below it within one of the flue-like members 24, and a similar series of tubular passages is provided in the lower portion of'said heating apparatus, the passages I95 and I96 being connected by means of the return bend I91, the passages I96 and I98 being connected by means of the return bend I99, the passages I98 and H9 being connected by means of the return bend III, the passages H2 and H9 being connected by means of the return bend I I3, the passages II2 and H4 being connected by means of the return bend H5, and the passages H4 and I I6 being connected by means of the return bend I I1. The various tubular members 42 in the fines 24 ar thus connected in series in a similar manner 'to those within the flues, or heating elements, 25, and an outlet or discharge pipe H8 is connected by means of a'union 89 and other suitable pipe fittings, with the passage I I6 in the last tubular member A2 7 7 It will thus be seen that the fluid heater is provided with a plurality of passages for the products of combustion, or other hot gases, passing from the combustion chamber 2| to the flue 33, and that said hot gases, or products of combustion, pass into heat transfer relation with the liquid in the chamber within the tubular walled vessel for the heat transfer medium a plurality of times and that the heat transfer medium is first heated within the said chamber within said vessel, or container, and is circulated through the same by the pump from the inlet connection 89 to the outlet connection 83 in a circuitous passage, and then passes through the pipe 84 and conduit 89 into the series of tubes 42 connected together in a manner such that the liquid passes first through the passage 9| in one direction, through the passage 92 in the opposite direction, and thus back and forth in'succession through the passages 94, 96, 98, 99, I99, I95, I93, I98, H9, H2, H4 and H6 to the discharge pipe H8. This provides a very thorough, complete and efficient, as Well as rapid transfer of the heat from the gases passing through the fines to the heat transfer medium, inasmuch as the pump and the fan, or blower, are operated simultaneously to cause rapid circulation of the gases, or products 'of combustion, and the liquid on opposite sides of Walls, that are heat conducting, and due to the fact that a preliminary heating of the liquid heat transfer medium takes place in the main body thereof in the heating vessel before passing through the series of tubes that are connected together end to end in the alternate fashion above described.

The pipe or conduit H8 leads to a T I29, which has a thermostatic element mounted therein, from which a cable I2I extends, having conductors therein, which are part of a controlling circuit to be explained below. The pipe I22 leads from the T I29 to a T I23, and a branch pipe I24 extends from the T I23 to a valve I25, which is manually operated, which is connected with the T I26 in the return pipe 64 through suitable conduit means I21 made up of pipe and fittings as shown. The return conduit 84 also has a T I28 provided therein, from which the suction connection 65 extends, a valve I29 controlling flow of liquid through the suction connection 65. With the valves I25 and I29 open it will be obvious that the liquid that is being heated will be shortcircuited so as to be re- -circulated by means of the pump through the heating apparatus to more rapidly increase the temperature thereof when this is desired. Normally the valve I29 would 7 be open and the valve I25 would be closed.

A pipe I39 leads to a T I3I, which has thermostatic means mounted therein, from which a conduit I32 containing a liquid extends to suitable temperature responsive controlling means, which will be described more in detail below, and from said T the pipe I33 leads through a pressure actuated valve I34 to a T I35, which is provided with a drain connection I36 having the drain valve I 31 controlling the same, and conduit means I38 made up of suitable pipes and fittings extends to an apparatus I39 that is heated by the liquid heat transfer medium, a return conduit I49 extending therefrom and communication between said return conduit I49 and the return pipe 64 being controlled by manually operated valve MI. The heated liquid heat transfer medium passes through the conduit I38.to the apparatus I39 at a predetermined pressure and returns at atmospheric pressure due to the provision of the vent I42 in the return pipe connection to the apparatus.

The filter 11 is provided with means within the same for periodically cleaning the same, which is operated by means of the handle I43, the par ticular cleaning means not being a part of this invention and not being shown. The filter is also provided with a suitable drain opening from which the drain pipe I44 leads. A drain pipe I45 is also provided extending from a T I46 interposed in the inlet conduit to the pump, dis-.- charge therefrom being controlled by means of the valve I41.

Means is provided for controlling the operation of the heating'apparatus, comprising the burners, the draft creating means and the liquid circulating means, said controlling means com.-

prising a pair of similar temperature responsive indicating and controlling instruments I48 and I49, which are mounted on the front wall I59 of .the housing 29, a switch I5I being also provided controlling the operation of said controlling devices I48 and I49, and the signal lights I52 and I53 being also provided for the purpose of indicating which of the two controlling and indicating devices I48 and 149 are in operation due to the setting of theswitch I5I. The combined indicating and controlling instruments I48 and I49 are provided, respectively, with combined indicating and movable contact elements I54 and I55 that cooperate with adjustable contacts I56 and 151, and I58 and I59, respectively, the contacts 156,151,158 and I59.beingadj ust ed so that the controlling device I48 will control the temperature towhichthe heat transfer medium is heated between a relatively low minimum and maximum above the temperature at which the same would become too immobile to be circulated by the pumping means provided, and so that the controlling device I49 will control the temperature to which the said medium is heated between a relatively high minimum and. maximum, which is a suitable temperature range for heating the apparatus I39 that is to be heated by said heat transfer medium.

Referring to Fig. 11 it will be noted that the c'ontroling devices I48 and I49, the switch II, signal lights I52 and I53, which constitute pilot lights, the contacts; I56, I51, I59 and I 59, and the movable contact members I54 and I55 are provided in a controlling circuit for various apparatus including the motors 68 and 34, and the burners 23. In said diagram the conductors I65 and. I6I are shown as extending from a 110 volt supplyline, which would ordinarily be an alternating current supply line, aswitch I62 controlling the connection between the conductor I 59 anda conductor. I63, and the conductor I6I and aconductor' I64. The conductor I63hasa branch I65extending: therefrom, whichleads to a thermostatic. switchingelementv I69, which is the element mounted in the T I29; the conductor 5'95 and the conductor I61 leading from said thermostatic element I66, being mounted in the conduit I2I. The conductor I61 is connected with conductors I68 and I69, which lead, respectively, to stationary contacts I10Jand I1I of a switching device which has movable contact" elements I12, I 13 and I 14- mounted on a suitable: insulating element I315, so as to be'insulated from each other, which ismounted to move with a plunger I15 of iron, serving'as' thearmature of an electro-magnet of the. solenoid type having a winding I11.

From the conductor I68 a branch I18 extends to a terminal I19 on the switch I5I, which is electrically connected with the movable contact member'IBB of said switch. The movable contact member I12 is adapted to bridge the stationary contacts I19- and I8! to connect the conductors I82and I83'with the conductor I63.

The conductor I82-leads to one end of the windmg 111' anda conductor I84 leads from the other end of said winding through a resistance I95 to movable contact element I81 is, of course, insulat'edfrom the movablecontact element I89. The contact elements I61 and I89 are adapted to be selectively engaged with stationary contacts I68 and I 89, or stationary Contacts I96 and I9I, dependent upon the position to which the switch I5l isadjusted. The stationary contact I89 has a conductor I 92connected therewith, from which the conductors I93 andlillextend, the conductor I93 leading to the pilot light, or signal lamp, I52, and the conductor I94 leading to the contact I55. A-conduct'or I95 extends from the stationary contact I88 to a terminal I95, with which the movable contact element I54 is electrically connected; A conductor I 91 extends from the stationary contact" I9 Iand connects this with the conductors I98 and I99, the conductor I 99leading to the. pilot-light; ortsignal lamp, I55, while the: conductor? I 98 leadsto: the. contact I 5.3. The contact I9'81isr: connected by means of the-conductor Zillfl withthesmovable contact element I55 leading to a terminal ZIlI, with which said movabl contact element I is connected. The contacts I51 and I59 are connected by means of the conductors 202 and 263 with the conductor 204 connected with the conductor I 84 and through the resistance I leading to the conductor I64. Conductors 295 and 286 extend from the signal lamps I52 and I53 to a conductor 291, which is connected with the conductor 294 to thus connect the signal lamp I52 or the signal lamp I53 in the circuit, dependent upon the position of the switching device I5I.

The temperature responsive element 288,,which is located. in the T I3 I, has the liquid conduit I32 having branches 299 and 2I9 leading therefrom to the indicating and controlling instruments I48 and M9. The internal construction and operation of said temperature responsive means comprising the element 299 and its connections with the devices I48 and I49 is not part of this invention, except to the extent that the position of both of the movable contact elements I 54 and I55 is dependent upon the temperature of the liquid engaging the element 298. The controlling device I48 is of such a character, and the contacts I56 and I51 are so set, however, that the element 298 will cause the movable contact ele ment I54 to engage the contact element I56 whenever the minimum of the low temperature range is reached and the contact element I51 whenever the maximum of the low temperature range is reached, while the controlling element I48" is of such a character that the heat responsive means 298' will move the movable contact element I55 so that it will engage the stationary contact I58 when the'minimum of the high temperature range is reached, and will engage the contact I 59'when the maximum of the high ternperature' range is reached. The temperature responsive switching element I55 isof such a character and is so adjusted that the same will move to open circuit position when a temperature is reached above the temperature at which the contact I55 engages the contact I59, but below the boiling point of the liquid that is to be heated, preferably, being set at 500 F. for the liquid that is at present preferred for heating the apparatus I39 that it is preferred to heat by said heat transfer medium.

With the switch I52 closed and the switch i5I being thrown to a position that the contactsv B81 and I88 engage, and the contacts I89 and I89 engage, when the minimum temperature for the low temperature range, or low temperature control, is reached, the contact element I54 will engage the contact element 555. However, n'o matter what'the position ofthe contact I54, the signal lamp I52 will be energized as soon as the switch is thrown into position to close the circuit between the contacts I89 and I89 and the contacts I81 and I58. With the contact I59 in engagement with the contact I56 the circuit will be completed'from the conductor I63 through the conductor I55, temperature responsive element I56; conductor I51, conductors I63 and I18 to' the contact I89, through the switch I5I, through the conductors I92 and I9 to thecontact I55; then through the movable contact member I54 and conductor I95 to the contact I83, through the switch I5I to the conductor E33, and through the winding I11, conductor I94 and resistance 55 to the conductor Hit. The winding I11 being energized, the plunger will be drawn upwardly into the winding until the movable contact ele'-' ment" I-l'Z-engages the contacts I19 and NH, thu

completing'the circuitfror'n the conductor I68 to the conductor I82 and thus maintaining the winding I11 energized even. though the movable contact I54 should leave the stationary contact I56, as will occur when the heating apparatus is in operation. Thus the Switch having the movable contacts I12, I13 and I14 will be held in circuit closing position whilethe movable contact element I54 is in engagement with the stationary contact I56 and after itleaves the same, 'until'said movable contact I54 engages the stationary contact I51. When this takes place, the circuit will be completed between the conductor I64 and the conductor I63, through the resistance I85, the conductor 264, the conductor 293; contact I51, contact I54, conductor !95 through the switch to the conductor I83 and through the contact I12 to the conductors I63 and I61,'and through the closed thermostatically controlled switching element I66 to the conductors I63 and I65, thus shunting,'or short-circuiting, the winding I11, whereupon the same will cease to attract the plunger I16 and the plunger will drop by gravity out of the winding I11 into open circuit position, thus disengaging the contact I12 from the contacts I19 and I8I. Said switching element also controls other apparatus, which will be described below.

When the switch II is thrown to the alternative position with the contacts I81 and I 99 in engagement and the contacts I80 and HM in engagement, the controlling element I49 will control the operation of the various apparatus of the heating means, and the pilot light, or signal lamp, I53 will indicate that the switch has been thrown to this position, as this will provide a connection between the conductor I18 and the conductor I99, as will be obvious, at the same time the connection between the conductor I18 and the conductor I93 will be broken, thus throwing the lamp I52 out of operation. With the contact I55 in engagement with the contact I55 and the switch I5I in said last mentioned position; the winding I11 will be energized due to the fact that the conductor I18 will be connected through the switching means with the conductor I98 leading to said contact I58, and the conductor 209 leading from the movable contact I55 will be connected with the conductor I 83 leading to the winding I11, thus energizing the winding in a similar manner to that previously described.

As soon as the winding is energized the switch ing element having the movable contacts I12, I13 and I14 will be moved to circuit closing position and the winding will continue to be energized in the same manner as previously described, even though the moving contact H55 leaves the stationary contact I58, and this will continue until the contact I59 is engaged by the contact I55. When this takes place, the winding I11 will be shunted or short-circuited in a similar manner to that previously described, due to the fact that the contact I59 is connected with the conductor 244 through the conductor 262 and the contact I55 is connected with the conductor I83 through the switch I5I. As soon as the winding is die-energized, the switching means controlled thereby will move to the open circuit position shown in Fig. 11.

The motors 68 and 34 are controlled'by a pair of switches having movable switching elements 2I I and 2 I 2, respectively, which are contro led in their operation by windings M3 and 2I4, respectively, so that when said windings are energized the switching means'will be moved to circuit closing position. Said switching means control the supply of current to the motors 68 and 34 from a, 229 volt three-phase supply line. The conductors 2I5, 2I6 and H1 lead into the switch having the movable switching element 2H and the conductors 2I8, 2I9 and 225 lead into the switch having the movable switching element 2I2. A conductor 22I leads from one of said supply lines to the stationary contact 222, which is connected with the stationary contact 223 by the movable contact'element I14, when the switch controlled by the winding I11 is in circuit closing position. A conductor 224 leads from the stationarycontact 223 to one contact 221 of an overload switch, which has a cooperating contact 228. A thermostatically controlled switching device 225 is bridged across the conductors 22I and 224 by means of conductors 349 and 226. The contact 228 is connected by means of the conductor 229,'with a normally closed manually operable switching element 235, which controls the connection between the conductor 229 and a conductor 23I leading to the winding 2M. From the winding 2I4 a conductor 232 leads to one contact 233 of an overload switch having a cooperating contact 234 and from said cooperating contact 234 a conductor 235 leads to the' manually controlled switching element 235, which is normally closed, and which controls the connection between the conductor 235 and a conductor 231 leading to the winding 2I3, which is connected with a conductor 2I6 by a conductor 238.

Thus, if the movable switching element I14 is in circuit closing position, both of the windings 2 I4 and 2I3 will be energized to move the movable switching elements 2 and 2I2 to circuit closing position, the movable contacts of which connect the conductors 215, 2I5 and 2H with the conductors 239, 245 and 24I leading to the motor 68, and the conductors 2I8, 2I9 and 220 with the conductors 242, 243 and 244 leading to the motor 34. Heating elements 245 and 246are interposed in the conductors 249 and 24I, respectively, to heat the fusible material 241 to move the contact 233 away from the contact 234 under the influence of the spring 248 when the motor 68 is overloaded. In a similar manner the heating elements 249 and 253 are interposed in the conductors 243 and 244 to separate the contact 221 from the contact 228 under the influence of the spring 248 when the motor 34 is overloaded. It will be noted that if either of the contacts 221 or 233 are moved to open circuit position, or if either of the manually operable switching members 239 or 236 are moved to open circuit position, as well as if thermostatic element 225, moves to open circuit position, both windings H3 and 2I4 will be de-energized and the switching elements 2i I and 2 I2 will move to open circuit position under the influence of a spring, or any other suitable member, thus halting the operation of the motors 34' and 68. Thethermostatically controlled switching element 225, for the particular liquid that, preferably, is used as a heat transfer medium, is so adjusted that the same will be closed. at a temperature. of 350 F. and will remain closed above that temperature, While the same will open below said temperature.

A stationary contact member 25I is provided, with which the contact member I13 engages when the movable switching element controlled by the .winding I11 is held in circuit closing position,

said contact I13 connecting the stationary contact I11 and the contact 25I when in such circuit closingzposi-tiom, A-conductor 252 extendsirom the-contact 25I to: as contact 2.53r-provided1inthe switch controlling-the mot-or 34,, a: movable ,com tactelement 254 of said: switch connecting said contact 253 and a contact1255 when, said switch-is in circuitclosing position, the contact 255-having a conductor 256 extending therefromethat leads to thecontact 251, which is engagedbt the movaable contact member=258 .-'provided onthe switch controlling the operation of the motor, 58 -t connectsaid contact 251 with the-stationary contact 259, from which the conductor 2601.,leads; to a contact 26I of a thermostatically controlled switch having a movable contact 262;- (see Fie, 9) said switch-beingpartof a-thermostatic control under the influence of the-pilot-ligh-tof one ofthe burners 23 the pilot lights being of any' desired character andbeing indicated, generally by; the numeral 263:in Figs.- Hand 12-, the; thermostatic element of the thermostatic switching means within range 1 of the pilot lights being indicated generallvoy the numeral ZM -aHdha-Ving; liquid conduits 255 leading therefrom to the-respective thermostatic switching elements;

A conductor 2'56 connects the two thermostatic switching elements252 in series andithe'contact 261" ofthe second of-said thermostatic switching elements is connected by -means of a conductor 26 1 with a windin 258 of an electro-magn-etically controlled, plunger -valve -269,- aicondu-ctor -2lll-=entending from said winding 258ntothe-conducto1: I64. Thus whenthecontacts HI, and 25,!31'6 bridgedby themovahle contact element ll3-by a closing of the magnetically operatedplunger switch, a circuitis-completed from the conductor ldlthrough the conductor; I65,,,thermostatically controlled, switching elementnlfifi; conductor I6], conductor I59, concluctor 252 switching clef mentv 255, conductor. 255, switching l elemehtl 2,58, conductor 269, thermostaticallycontrolled:switch-r ing elements 262, conductor ZGLand conductor 21 3, to the conductor-ISA, and. if ,theiswitch l62ls closed the 110 volt current supply will operate to energize the Winding 258 to open-the plunger valve mechanismZfiS to supplygas :tothe burners 23in a, manner. to :be. described below.

However, this circuit. will notbe completed and the burners will not be supplied with gas-if either of the pilot lights isnotfunctionina aiSIODB or both of the thermostatic switching elements 252 willbe in. open circuit position... Alsothe burners 23 will not be, supplied, with gas if the switchingelements 2H and 212 arenot. in circuit closing position, as the-circuit.wil1 be broken at the, movable, contact. members 258 andv 254: Thesame would be true iii either ofthesewcrenot in circuit closinapositiona In addition to this, the thermostatic element 22 has, to be-in circuit closing position. For, the. liquidthat is utilized as a heat transfer medium forheating the apparatus i353, thecontacts. I56Jand I5'Lare set so that the controlling device; Ifiwill maintain the liquid at atemperatureofhetween 250 and 360 F. to keep thersameinacompletelyliq uid' condition... The, contactsiil 58. and I 59 areeset to maintain the operating, temperature of the liquid betweenABO" anddlfifi" F; thisubeingthe preferred temperature at .whichtoloperate the apparatus I39. The thermostatic element 225is set toclose at 350, Hand; remainclosed above that temperature, while the thermostaticelement l55is settoopen at 5063 andremain open abovethattemperature,

As a, result, under normal; Operating; condi tions, when the, control device I 494s functioning;

the switching; element: controlledlas -the?v winding I H will merelvtum; thegaszto the. burners I 23 on: and off; dependent on whether the contact I is in engagement with; the contact I58 or-with the contact I59, .this being due ;to..the= fact that the thermostatic: element 225 is; set: at. such a temperaturethat the circuit controllingthe supply of current tothe windings. 2I3tand Zld will keep the switching/elements- 2:I I i and 12 I 2: in: circult, closing position; keeping the motorsfiu-and 34- in :operation,, but-.the connection between the contacts I I I and 25 I will be ibrokenuto ,causethe valve 269 to be closed,,; ,thus ;,closing; ,off, thesupply of gasto the {burners 235 am nnertoei-described below.

However, when: the low; temperature control I 48* is in operation :it will icontrolthe; operation of thBQmOtOIS, I58 and: 34* andthe: burners 23;v so that the burnerscannot operateuntil the motors 34- andfiB have had their operating circuitsclosed due t0;the-operation..of the switching elements 2 and 212, butt-said switching-elementsJII and 2 I 2 will move between open andclosingapositions along; with the switching elements controlled aby the winding II'I whenever; the contact: I541 en: gages'the contactzl51;and whenever the contact I54 engagesthecontact" I56. Ofncoul'se; it'is'to be understood that in themase: .of the: controlling device 148,. the motorsand the burners ;will con;- tin-ue to operate, as; the: moving con-tact I54 moves to the right due tothe=fact that the liquid is being heatedqby; the,heating. apparatus., and will continue untilithet contact I55-engages the contact l 51; while ,in the:acasev.of the controlling. device M9 the burners; will i continue-Etc; operate after: the contact I 55-lea-ves the contactiI 58; until-=itengages the contact I59j due tovthaliquid having been 2, heatedv by' the heating; apparatus; but that the motors-will continue tofunctionto drawheat out-of-the combustion-chamber, until the burners again go on; ShouId-Lthe switchin means comprising the; movable: contact element I55 iailto function-to shut off the burnerswhenthe same engages the contact I 59; the thermostatic element Ifi-figwill:breakthe-controlling circuit for the burners when the temperature reaches-500 F.

Thegas-supply pipe; ormain gasline; isindicated-bythe numeral 2"II-. Said gas-line leads to the diaphragm valve- 212' shown more inv detail in- Fig. 9. Said valve has a valve--.memberr2l3, whichuis' seated-by-means Ora-spring 214- against a-valve seat 215-; the position of' said valve meme her being determined by means of, a: diaphragm 216 mounted ina, chamber havingawall 2'IIextending from: the upperportionot the upper valve -body-2'l8, anda cover. member 229: com: pletingzthe diaphragm chamber, the diaphragm being: clampedqbetweem flanges on the members 21 I and 219411 a well-known manner; and .aguide zsnibeing provided -forthe valve, stem; 281 in the cover member 219:- A! chamber 28 2inthe valve member 212 is connected-,with the: gas; supply pipe-- 21 I andabwpasslfiii:leads-iromsaidzchame her- 282 to the-pipenk, said-pipe;leading;:into a. chamberzsli; whichleadsto the; valve seat 285; which, is engaged' by 'the' plungerxvalve 28'! when the same isin closingposition; said valvebeingheld, in closing positionv by the. weight* of; the plunger 288'; which constitutes; a-movable core orarm-ature for the solenoid or winding (253," and: is drawn, upwardly: when ,;the winding: 258 is ener. ized to: open the passage, between 1- the chamber 3 285;- and a chamber, 289-, from which thcrnipexlsua leads to a passage 29I in the valve body 218, said passage leading into the chamber 292 under the diaphragm 216, said passage being of an annular character, as will be obvious from Fig. 9.

'The gas entering the chamber 292 will gradually cause the diaphragm 213 to be raised, thus graduallly lifting the valve 213 from its seat to gradually open the passage between the chamber 282 and the chamber 293 in the valve 212. The chamber 293 is connected with the burner supply pipe 294, which supplies gas to the burners 23 through the branches 295, which may be provided with manually operated valves 293 for shutting on either or both said burners manually, should this be desired. Primary air mixers 291 and secondary air mixers 298 are provided a for said burners, and as will be evident from Fig. 12. Said burners have a box-like refractory portion 299 mounted on the forward ends there of within the refractory wall of the combustion chamber 2I, said refractory box-like members being mounted in suitable metallic frames 3% forming a part of said burners, a flaring passage 30"] being provided in each burner leading into I the combustion chamber 2 I.

' A branch pipe 302 extends from the main gas supply pipe 21I to a T 393, from which the branch ipes 384 extend to pilot lights 263. Thus gas is supplied to the pilot lights as long as the main supply pipe 21I is being supplied with gas, and said pilot lights are being kept constantly in operation. To assure such constant operation of 'said pilot lights and to re-ignite the same in case the gas supply should get too low to properly operate the pilot lights, or be interrupted, spark plugs 305 are provided located in such position relative to the pilot lights that the gas passing therefrom would be ignited promptly by said spark plugs. The spark plugs are operated by a timer mechanism 386, which is connected with the conductors I63 and I64 by means of the conductors 301 and 388, said timer having a movable contact element 3119, which alternately engages the stationary contacts 3H) and 3! I, from which the conductors 3I2 and 3I3 lead to the spark plugs so that a high tension current is supplied to each spark plug alternately, the high tension current being supplied by an induction coil having the primary winding 3M connected with the conductors I63 and I64 by the conductors 3I5 and 3I6, and having a secondary winding 3I1 that is grounded at one end thereof in the usual manner and connects with the moving contact 389 throughthe conductor 318 at the other end thereof.

The diaphragm valve 212 is provided with means for venting or discharging the gas from the chamber 292 under the diaphragm when the winding 268 is de-energized and the plunger 288 drops into the position shown in Fig. 9. When this position of the valve is reached, the beveled face 3 I9 of the valve member disengages the seat 323 controlling communication between the chamber 289 and a chamber32l, which has a passage'322 extending therefrom connected with thevent pipe 323, which leads into the combustion chamber, so that any gas that is vented from under the diaphragm will escape into the combustion chamber and not into the room. It will be obvious that with the valve in the position shown in Fig. 9, the conduit 289 leading from the chamber 292 will be connected with the vent pipe 323 and the pressure under the diaphragm will be relieved, causing the spring 214 to seat the valve 213 and shut off the main gas supply. In order to control the rate of opening of the valve 213 an adjustable pin-like member 324 is provided, which is adapted to be moved toward and away from the orifice in the union 325 connecting the pipe 284 with thebody portion of the member having the chamber 285 therein. Thus the rate of discharge of gas into the chamber 285 will be controlled by the position of the member 324, which will determine the rate at which the chamber 292 is filled thereby sufficient ly to raise the valve 213 to wide open position.

The mounting of one of the thermostatic elements in the system is illustrated in Fig. 10, the thermostatic element shown being that provided in the T 15, which connects the pipes 61 and 18. A special plug-like member 326 is mounted in the T 15 and a bushing 321 is provided for connecting the conduit 18 liquid-tight with said plug 323. The conductors 324 and 228 are mounted in the conduit 18 and extend in a tubular member 328 to the thermostatic switching device 225, which is'provided with a suitable heat responsive element Within the same, the particular construction of which is not a part of this invention. The thermostatic means, it will be noted, is in this manner mounted directly within the stream of liquid passing from the pipe 81 through the T into the pipe 16 and will be affected directly by the temperature of said liquid. The other thermostatic element I66 is similarly mounted, and a similar mounting is provided for the heat responsive means 208 in the T I3I.

A valve 329 is provided in the pipe 522 to control flow of liquid therethrough, so that if it is desired to dismantle any of the piping and maintain the liquid within the heating device, this can be done by moving the valve 329 to closing position. A T 330 in the conduit 19 may be provided with a drain pipe connection 33I controlled by a drain valve 332, so that liquid can be drained from this conduit 19 if desired. The drain pipe I44 on the filter is also provided with a valve 333, as will be obvious. The pilot lights may be provided with valves 334 for shutting these off when the apparatus is not in use at all. However, ordinarily, the pilot lights are kept constantly in operation.

The pump and the motor therefor are, preferably mounted on a suitable platform 335 on the housing portion 28, a suitable mounting 335 being provided for the bearings for the shaft 38. The electrical supply lines, preferably, enter through a conduit 331, which runs to a panel board 338, upon which the various switches are mounted in suitable housings as shown, the particular location of the switches on the panel board being immaterial to the invention. In addition to the pressure gauge 81, a pressure gauge 339 is, preferably, provided on the front wall I50, so that the pressure and temperature arereadily readable from the front of the device. A liquid heat transfer medium suitable for use in my circulatingliquid heater is a special petroleum distillate that has a a flash pointof 550 F. and a fire point of 620 F.

In operation, the controlling device i l-9 will be adjusted permanently for the minimum and maximum operating temperatures of the liquid heat transfer medium that it is desired to heat with the apparatus, and the pilot lights being once put in operation, the valves leading to the same will be left constantlyopen and the switch I 62 will be kept constantly closed. With this condition existing, engagement of the movable con-' tact member I55 with the contact member I58 when the liquid is at or below the minimum operating temperature will close the magnetically controlled switch having the winding I11, which will close the switching elements 2 and 2I2 to set the motor 68 and 34 in operation, and will also set the burners 23 in operation, provided the pilot lights are in operation. This operation of the burners and the motors 68 and 34 operating the pump 68 and the fan 32, respectively, will continue until the maximum operating temperature of the liquid is reached, whereupon the movable contact member I55 will engage the contact member I59, causing the plunger I18 of the magnetically controlled switch to drop to open circuit position, whereupon the burners 23 will be thrown out of operation through the release of the plunger 288 by the solenoid, or winding, 258. However, the motors 34 and 88 will continue to operate the fan, or blower, and the pump, because the thermostatically controlled switching means 225 will remain closed between the minimum and maximum operating temperatures, and even above the minimum and maximum operating temperatures. Thus the draft will continue to be created and the liquid will continue to be circulated through the heater, causing all of the heat that is in the combustion chamber and refractory walls to be transferred to the liquid heat transfer medium. This will continue as long as the heat transfer medium at operating temperatures is to be supplied to the apparatus I39, the burners 23 being switched on and oif, dependent upon whether the contact member I55 engages the contact member I58 or the contact member I59, but the fan and pump continuing to operate whether the burners are on or off.

When it becomes time to shut off the apparatus I39, the switch II' is thrown from the position, with the contacts I81 and I 88 in engagement with the contacts I90 and I9I, to the alternative position, with the contacts I81 and I88 and the contacts I88 and I89 in engagement, the switch being of such a character that it can only assume either a position in engagement with the contacts I98 and I9I, or in engagement with the contacts I88 and I89. The controlling element I48 is then thrown into operation by this movement of the switch I5I,

and this controlling element continues in operation until the switch is thrown into the alternative position again. While the controlling ele ment I48 is controlling the operation of the device, the temperature will at first be dropping from the higher operating temperature to the low temperature maintained by this controlling element I48, and the fan and pump will be kept in operation due to the fact that the motors 34 and 93 will not be thrown out of operation when the shift is made to the low temperature control I48, inasmuch as the thermostatic element 225 will remain closed until a temperature of 350 F. has been reached in the downward drop of the temperature from operating temperatures. At this time the contact I54 will be in engagement with the contact I51. However, by operating the fan and pump during this time, the heat will be extracted from the combustion chamber and the walls of refractory material to utilize the heat stored in these walls to maintain the heat transfer medium in a liquid, mobile condition, saving gas or other fuel and preventing the operation of the low temperature control unnecessarily. After the temperature drops below 350 F. the motors 34 and 68 will be shut off due to the action of the switching elements 2 and 2I2 responding to the break in the circuit by the thermostatic element 225, and will notagain be started until the contact I54 engages the contact I55, whereupon said motors will again be started and the burners thrown into operation in the manner previously described and will continue in operation until the liquid has been heated to such a temperature that the contact I54 will engage the contact I51. When the contact I54 engages the contact I51 the burners, as Well as both motors, will be discontinued in operation due to movement of the switch contacts I12, I13 and I14 to open circuit position, the thermostatic element 225 no longer keeping the circuit controlling the windings H3 and 2 I4 closed, irrespective of the position of the switching element I 14.

"While the tank 52 is vented in the manner already described, and the apparatus I39 is vented at I42, there is a possibility that the rapid cooling of the heat transfer liquid in the apparatus I39 when the pump ceases operation, may cause a partial vacuum to be developed in the heat transfer liquid supply pipe I38, which could withdraw liquid from the heating device due to the creation of this vacuum, if it were not for the check valve I34, which is a spring loaded valve that responds to a pressure of five pounds to the square inch or more, so that the same will open when the pump is in operation, but will remain closed to prevent such action whenthe pump is not in operation. As heretofore explainedthe burners 23 will not go into operation if the pilot lights are out, and will be thrown out of operation by the thermostatic means I93, if the temperature exceeds the maximum operating temperatureto an undesirable extent. Also, if a decrease in pressure takes place, or an interruption in pressure takes place in the gas, and then the pressure again increases and the pilot lights should have gone out because of this variation in pressure of the gas, the spark plugs provided will immediately re-kindle the pilot lights. The apparatus is accordingly substantially automatic in operation and safe, and is also substantially self-contained, being 'so mounted that the same can be transported as a unit and installed in a laundry, or other similar place, and connected with the apparatus that is to be heated by the heat transfer medium in a simple manner without requiring any particular knowledge as to the details of construction of the apparatus.

What I claimis:

1. A- heater of the character described, comprising a fluid-tight vessel, means for supplying fluid to be heated thereto, a plurality of conduits for the products of combustion extending through said vess'eL fluid conduits connected with said vessel to receive fiuid therefrom, said fluid conduits extending within said conduits for the products of combustion, and means for mounting said fluid conduits in spaced relation to said conduits for the products of combustion, comprising a plurality of radial fins constituting heat conducting walls connecting said conduits for the products of combustion and said fluid conduits, said fins extending continuously longitudinally between said conduits.

2. A heater of the character described, comprising a fluid-tight vessel, a combustion cham-, her at one end thereof, a stack, flues mounted lengthwise in said vessel in fluidtight relation therewith and communicating with said combustion'chambe'r and stack, means connecting said fines to lead the products of combustion through said vessel a plurality of times from said combustion chamber to said stack, inlet means for supplying fluid to be heated to said vessel near one end and near the bottom thereof, fluid conduits mounted in said flues and connected with said vessel near the top and near the other end thereof, means directing 'flow of said fluid to engage said fluid a plurality of times with said flues in passing from said inlet to the connection with said fluid conduits, a discharge conduit connected with said fluid conduits, means connecting said fluid conduitslto lead the fluid therein through said flues a plurality of times from said vessel to said discharge conduit, and means for circulating said fluid toflow through said inlet and said fluid conduits at a rapid rate. 7

- 3. A heater of the character described, comprising a fluidtight vessel, a combustion chamber at one end thereof, a stack, flues mounted lengthwise in said vessel in fluidtight relation therewith, said flues comprising a lower set communicating with said combustion chamber and an upper set communicating with said stack, means connecting said flues of one set with those of the other set to lead the products of combustion through said vessel a plurality of times from said combustion chamber to said stack, inlet means for supplying fluid to be heated to said vessel near one end and near the bottom thereof, fluid conduits mounted in said flues, said fluid conduits being all connected in a single series, th first of said series being connected with said vessel near the top and near the other end thereof, means in said vessel providing a circuitous path for said fluid between said inlet means and the connection for said fluid conduits therewith, a discharge conduit connected with the last fluid conduits of said series, and means connecting each of said fluid conduits with the next conduit of said series to lead the fiuid'therein successively first through the flues of said upper set and thenthrough the flues of said lower set and to said discharge conduit.

1 4. A heater of the character described comprising a vessel, mean for passing liquid to be heated through said Vessel in a circuitous path, a combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, and means for receiving the liquid from said Vessel and conducting the same back and forth in a circuitous path a multiplicity of times into heat transfer relation with the products of combustion in the means for passing said products of combustion into heat transfer relation to the contents of said vessel.

5. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel in a circuitous path, comprising liquid circulating means, temperature responsive means controlling the operation of said liquid circulating means, a combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, and means for receiving the liquid from said vessel and conducting the same in a circuitous path a multiplicity of times into heat transfer relation with the products of combustion in the means for passing said products of combustion into heat transfer relation to the contents of said vessel. l

' 6. A heater of the character described com prising a vessel, means for passing liquid to be heated through said vessel in a circuitous path, a combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, comprising draft creating means, temperature responsive means controlling the operation of said draft creating means, and means for receiving the liquid from said vessel and conducting the same in a circuitous path into heat transfer relation with the products of combustion in the means for passing said products of combustion into heat transfer relation to the contents of said vessel.

'7. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel in a circuitous path, comprising liquid circulating means, a combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, comprising draft creating means, temperature responsive means simultaneously controlling the operation of said draft creating means and said liquid circulating means to circulate-said liquid only while said draft is being created, and means for receiving the liquid from said vessel and conducting the sam in a circuitous path into heat transfer relation with the products of combustion in the means for passing said products of combustion into heat transfer relation to the contents of said vessel.

8. A heater of the character described comprising a vessel, means for passing liquid to be heatedthrough said vessel in a circuitous path, comprising liquid circulating means, a combustion chamber, means for passing products of combustion from said chamber into heat trans ferirelation to the contents of said vessel a plurality of times, comprising draft creating means, a plurality of temperature responsive means operating over different temperature ranges simultaneously controlling the operation of said draft creating means and said liquid circulating means to circulate said liquid only while said draft is being created, means for selecting one of said temperature responsive controlling means and means for receiving the 1iquid from said vessel and conducting the same in a circuitous path into heat transfer relation with the products of combustion in the means for passing said prodnets of combustion into heat transfer relation to the contents of said vessel.

9. A heater of the character described comprising a vessel, means for passing liquid to be heated through said Vessel in a circuitous path, comprising liquid circulating means, a combus tion chamber, fuel-burners in said combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, comprising draft creating means, means for receiving the liquid from said vessel and conducting th same in a circuitous pathinto heat transfer relation with the gases in the means for passing said products of combustion into heat transfer relation to the contents of said vessel, and temperature responsive means controlling the operationv of said burners, said draft creating means and said liquid circulating means comprising means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures, means for throwing said operating means into and out of operation, and means for operating said draft creating means and said liquid circulating means independently of said burners to transfer heat from said combustion chamber to said liquid after throwing said first operating means out of operation.

10. A heater of the character described comprising a Vessel, means for passing liquid to be heated through said vessel in a circuitous path, comprising liquid circulating means, a combustion chamber, fuel burners in said combustion chamber, means for passing products of combus tion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, comprising draft creating means, means for receiving the liquid from said vessel and conducting the same in a circuitous path into heat transfer relation with the gases in the means for passing said products of combustion into heat transfer relation to the contents of said Vessel, and temperature responsive means controlling the operation of said burners, said draft creating means and said liquid circulating means comprising means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of th liquid between predetermined minimum and maximum temperatures much higher than the boiling point of water, means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures much lower than said first mentioned temperatures, temperature controlled mean for throwing each of said operating means into and out of operation, and means for selecting either of said temperature controlled means for controlling said operatini; means.

11. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel in a circuitous path, comprising liquid circulating means, a combustion chamber, fuel burners in said combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel aplurality of times, comprising draft creating means, means for receiving the liquid from said vessel and conducting the same in a circuitou path into heat transfer relation with the gases in the means for passing said products of combustion into heat transfer relation to the contents of said vessel, and temperature responsive means controlling the operation of said burners, said draft creating means and said liquid circulating means comprising means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures much higher than the boiling point of water, means for operating said burners, draft creating means and fluid circulating means in unison to maintain the tem perature of the liquid between predetermined minimum and maximum temperatures much lower than said first mentioned temperatures, temperature controlled means for throwing each of said operating means into and out of operation, means for selecting either of said temperature controlled means for controlling said operating means, and means for operating said draft creating means and said liquid circulating means independently of said burners to transfor heat from said combustion chamber to said liquid after throwing said first operating means out of operation.

12. In a device of the character described, means for heating a liquid, apparatus heated by said liquid, and means for circulating said liquid between said heating means and said apparatus, said liquid having a much higher boiling point than water and being of insufficient mobility to be circulated at atmospheric temperatures, said heating means comprising controlling means for maintaining said liquid at a temperature between a minimum and a maximum required to heat said apparatus to an operating tempera ture, controlling means for maintaining said liquid at a temperature sufilcient to maintain the mobility of said liquid to permit circulation thereof, but lower than said minimum, and means for selecting either of said controlling means.

13. In a device of the character described, means for heating a liquid, apparatus heated by said, liquid, and means for circulating said liquid between said heating means and said apparatus, said liquid having a much higher boiling point than water and being of insuflicient mobility to be circulated at atmospheric temperatures, said heating means comprising controlling means for maintaining said liquid at a temperatur between a minimum and maximum required to heat said apparatus to an operating temperature, controlling means for maintaining said liquidiat a temperature sufficient to maintain the mobilit of said liquid to permit circulation thereoflbut lower than said minimum and means for selecting either of said controlling means, said heating means comprising means for passing hot gases into heat transfer relation to said liquid, and said controlling means comprising temperature responsive means for simultaneously throwing the means for passing said gases and the circulating means into and out of operation.

14. In a device of the character described,means for heating a liquid, apparatus heated by said liquid, means for circulating said liquid between said heating means and said apparatus soithat said liquid passes from saidheating means to said apparatus under a pressure higher than atmospheric and returns from said apparatus at atmospheric pressure comprising a vented receiver, a pump between said receiver and said heating means, a feed line extending from said heating means into said apparatus, and a vented return line extending from said apparatus to said receiver.

15. A heater of the-character described comprising a vessel, means for passing liquid to be heated through saidvessel in a circuitous path, comprising liquid circulating means, a combustion chamber, fuel burners in said combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, comprising draft creating means, means for receiving the liquid from said vessel and conductin the same in a circuitous path into heat transfer relation with the gases in the means for passing said products of combustion into heat transfer relation to the contents of said vessel, and temperature responsive means controlling the operation of said burners, said draft creating means and said liquid circulating means comprising means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures, said meansfcr operating said burners comprising pilot lights, a valve controlling the supply of fuel to said burners, means for opening said valve, and means preventing said operating means from opening said valve except when said pilot lights are burning.

16. A heater of the character described cornprising a vessel, means for passing liquid to be heated through said vessel in a circuitous path, comprising liquid circulating means, a combustion chamber, fuel burners in said combustion chamber, means for passing products of com-- bustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, comprising draft creating means, means for receiving the liquid from said vessel and conducting the same in a circuitous path into heat transfer relationwith the gases in the means for passing said products of combustion into heat transfer relation to the contents of said vessel, and temperature responsive means controlling the operation of said burners, said draft creating means and said liquid circulating means comprising means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maxi mum temperatures, said means for operating said burners comprising pilot lights, a valve controlling the supply of fuel to said burners, igniting means for said pilot lights operating at closely spaced intervals independently of said operating means, means for opening said valve, and means preventing said operating means from opening said valve except when said pilot lights are burning.

17. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel in a circuitous path, comprising liquid circulating means, a combustion chamber, fuel burners in said combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, comprising draft creating means, means for receiving the liquid from said vessel and conducting the same in a circuitous path into heat transfer relation with the gases in the means for passing said products of combustion into heat transfer relation to the contents of said vessel, and temperature responsive means controlling the operation of said burners, said draft creating means and said liquid circulating means comprising means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures, means for throwing said operating means into and out of operation, and temperature responsive means for throwing said burner out of operation at a predetermined temperature above said maximum and below the boiling point of the liquid. i a

18. A heater of the character described, com

prising a horizontally elongated fluid tight vessel, means for supplying liquid to be heated thereto to maintain said vessel completely filled therewith, comprising a liquid inlet leading into the bottom of said vessel near one end thereof, a liquid outlet leading from the top of said vessel near the other end thereof, a plurality of conduits for the products of combustion extending lengthwise through said vessel, baffles in said vessel directing said liquid to follow a circuitous path and into engagement with each of said conduits a plurality of times between said inlet and outlet, and a plurality of liquid conduits connected alternately at opposite ends thereof in a single series, one end of said series being connected with said vessel to receive'liquid from said liquid outlet, said liquid conduits extending lengthwise within said conduits for the products of combustion, the other end of said series being connected with a heated liquid discharge conduit.

19. A liquid heater, comprising a horizontally elongated fluid tight vessel, a plurality of fiues extending longitudinally through said vessel from end to end thereof, a liquid inlet entering through the bottom of said vessel near one end thereof, a liquid outlet leading from the top of said vessel near the other end thereof, a plurality of vertical baffles in said vessel between said inlet and outlet arranged in alternating sets, the baffles of one set extending to the bottom of said vessel and being terminated short of the top thereof, and the bafiles of the other set extending to the top of said vessel and terminating short of the bottom thereof, and means for creating a forced circulation of liquid through said vessel from said inlet between each pair of adjacent battles to said outlet.

20. Aliquid heater, comprising a horizontally elongated fluid tight vessel, a plurality of iiues extending longitudinally through said vessel from end to end thereof, a liquid inlet entering through the bottom of said vessel near one end thereof, a liquid outlet leading from the top of said vessel near the other end thereof, said vessel being completely filled with liquid, means for directing circulation of liquid through said vessel from said inlet to said outlet in a circuitous path, a continuous circuitous liquid conduit extending from said outlet through all said fiues, comprising a length of conduit in each of said fines, and means connecting adjacent lengths alternately at opposite ends of said vessel to carry said liquid back and forth through one flue after another, and means for creating a force circulation of liquid through said vessel from said inlet to said outlet and successively through said lengths of conduit from end to end of said circuitous liquid conduit.

21. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel in a circuitous path, comprising liquid circulating means, a combustion chamber, fuel burners in said combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, comprising draft creating means, means for receiving the'liquid from said vessel and conducting the same in a circuitous path into heat transfer relation with the gases in the means for passing said products of combustion into heat transfer relation to the contents of said vessel,

and temperature responsive means controlling the operation of said burners, said draft creating means and said liquid circulating means.

22. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel in a circuitous path, comprising liquid circulating means, a combustion chamber, fuel burners in said combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel a plurality of times, comprising draft creating means, means for receiving the'liquid from said vessel and conducting the same in a circuitous path into heat transfer relation with the gases in the means for i passing said products of combustion into heat the operation of said burners, said draft creating means and said liquid circulating means comprising means for operating said urners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures much higher than the boiling point of water, means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures much lower than said first mentioned temperatures, temperature controlled means for throwing each of said operating means into and out of operation, means for selecting either of said temperature controlled means for controlling said operating means, and means for continuing said draft creating means and said liquid circulating means in operation after said last mentioned operating means has been selected until a predetermined temperature drop in said liquid below said higher minimum has occurred.

23. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel, comprising liquid circulating means, a combustion chamber, means for passing products of combustion from said chamber intoheat transfer relation to the contents of said vessel, comprising draft creating means, a plurality of temperature responsive means operating over different temperature ranges simultaneously controlling the operation of said draft creating means and said liquid circulating means to circulate said liquid only while said draft is being created, means for selecting one of said temperature responsive controlling means and means for receiving the liquid from said vessel and conducting the same in a circuitous path into heat transfer relation with the products of combustion.

24. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel, comprising liquid circulating means, a combustion chamber, fuel burners in said combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel, comprising draft creating means, means for receiving the liquid from said vessel and conducting the same in a circuitous path into heat transfer relation with said products of combustion, and temperature responsive means controlling the operation of said burners, said draft creating means and said liquid circulating means, comprising means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures, means for throwing said operating means into and out of operation, and means for operating said draft creating means and said liquid circulating means independently of said burners to transfer heat from said combustion chamber to said liquid after throwing said first operating means out of operation.

25. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel, comprising liquid circulating means, a combustion chamber, fuel burners in said combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel, comprising draft creating means, means for receiving the liquid from said vessel and conducting the same in a circuitous path into heat transfer relation with said products of combustion, and temperature responsive means controllingthe operation of said burners, said draft creating means and said liquid circulating means, comprising means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures much higher than the boiling point of water, means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures much lower than said first mentioned temperatures, temperature controlled means for throwing each of said operating means into'and out of operation, and means for selecting either of said temperature controlled means for controlling said operating means.

26. A heater of the character described comprising a vessel, means for passing liquid to be heated through said vessel, comprising liquid circulating means, acombustion chamber, fuel burners in said combustion chamber, means for passing products of combustion from said chamber into heat transfer relation to the contents of said vessel, comprising draft creating means, means for receiving the liquid from said vessel and conducting the same in a circuitous path into heat transfer relation with said products of combustion, and temperature responsive means controlling the operation of said burners, said draft creating means and said liquid circulating means, comprising means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures much higher than the boiling point of water, means for operating said burners, draft creating means and fluid circulating means in unison to maintain the temperature of the liquid between predetermined minimum and maximum temperatures much lower than said first mentioned temperatures, temperature controlled means for throwing each of said operating means into and out of operation, means for selecting either of said temperature controlled means for controlling said operating means, and means for operating said draft creating means and said liquid circulating means independently of said burners to transfer heat from said combustion chamber to said liquid after throwing said first operating means out of operation.

27. A liquid heater of the character described, comprising a horizontally elongated tank-Like vessel having inlet and outlet connections near opposite ends thereof, a combustion chamber at one end thereof, a chamber at the other end thereof, a lower set of lines extending from said combustion chamber to said other chamber, a stack chamber over said combustion chamber, an upper set of flues connecting said other chamber and said stack chamber, a stack, means for creating a draft in said stack, liquid circulating tubes mounted centrally in the flues of both sets, means connecting one of said liquid circulating tubes with said outlet connection, a discharge pipe, means connecting another of said liquid circulating tubes with said discharge pipe, means connecting all said liquid carrying tubes in a series to carry said liquid back and forth in said lines through said tubes, a pump discharging into said inlet connection to circulate said liquid through said vessel and said tubes, and common temperature responsive controlling means for said pump and draft creating means.

ing a pair of conduits extending upwardly there- .from above the top of said heating means, a receptacle connected with the upper ends of said conduits, and a continuously open vent tube extending from the top of said receptacle, and a pump between said receiver and said heating means.

29. In a device of the character described, means for heating a liquid comprising a heating ,vessel and a circuitous heating conduit both filled with said liquid, apparatus heated by said liquid, means for circulating said liquid between said heating means and said apparatus so that said liquid passes from said heating means to said apparatus under a pressure higher than atmospheric and returns from said apparatus at atmospheric pressure comprising a vented receiver, a

pump between said receiver and said heating means, and an unvented supplyline between said heating means and said apparatus; r

30. A' liquid heater of the character described, comprising a fluid tight vessel, means for supplying liquid to be heated thereto to maintain said vessel completely filled, means for directing said liquid through said vessel in a circuitous path, a plurality of conduits for the products of combustion extending through said vessel, and liquid conduits connected with said vesselto receive liquid therefrom after said liquid has passed through said vessel in said circuitous path, said liquid conduits being connected in series and extending within said conduits for the products of combustion.

31. A liquid heater of the character described, comprising a fluid tight vessel, means for supplying liquid to be heated thereto to maintain said vessel completely filled, a plurality of conduits for the products of combustion extending lengthwise through said vessel from end to end thereof, bafiies in said vessel extending alternately from the top and bottom thereof to direct said liquid to follow a circuitous path and into engagement with each of said conduits a plurality of times and a plurality of liquid conduits connected in series, one end of said series being connected with said vessel to receive liquid therefrom after said liquid has passed through said vessel in said circuitous path, said liquid conduits extending lengthwise within all said conduits for the products of combustion.

JOSEPH B. SANDO. 

